CN1319781A

Movatterモバイル変換

Info

Publication number: CN1319781A
Application number: CN01112073A
Authority: CN
Inventors: 山崎舜平; 小山润; 须泽英臣; 小野幸治; 荒尾达也
Original assignee: Semiconductor Energy Laboratory Co Ltd
Current assignee: Semiconductor Energy Laboratory Co Ltd
Priority date: 2000-03-27
Filing date: 2001-03-27
Publication date: 2001-10-31
Anticipated expiration: 2021-03-27
Also published as: CN1197141C; CN100397218C; TW513753B; SG94792A1; US20010052950A1; US7218361B2; KR20010090590A; CN1598677A; JP4712208B2; US7486344B2; JP2001345453A; MY135655A; US20070138480A1; KR100811583B1

Abstract

A highly reliable semiconductor display device is provided. A semiconductor layer in a semiconductor display device has a channel formation region, an LDD region, and source and drain regions, and the LDD region overlaps with a first gate electrode with a gate insulating film interposed therebetween.

Description

Semiconductor display device and preparation method thereof

The present invention relates to the semiconductor display device, the especially liquid crystal display device that use semiconductor element (semiconductor film membrane component).And, the present invention relates to the electronics equipment that uses semiconductor display device in the display part.

Form semiconductive thin film (thick for several) on the substrate of insulating surface and receive publicity having with the recent years of making thin film transistor (TFT) (TFT) to hundreds of nm.Thin film transistor (TFT) is widely used in electron device such as IC and semiconductor display device, and has obtained rapidly development, in particular for liquid crystal display device as on-off element.

The pixel portion of active matrix liquid crystal display device is made up of a plurality of pixels, and each pixel contains TFT and liquid crystal cell.Liquid crystal cell has pixel electrode, to electrode (opposingelectrode) and be formed on pixel electrode and to the liquid crystal between the electrode.Control can be at the pixel portion display image by the voltage of pixel TFT supply pixel electrode.

Particularly, can obtain high mobility as the active layer (crystal TFT) of TFT, therefore functional circuit can be integrated on the same substrate, thereby realize the liquid crystal display device that high-definition image shows with the semiconductor film of crystal structure.

The semiconductor film that has crystal structure in this instructions comprises single crystal semiconductor, poly semiconductor and crystallite semiconductor, also comprises the semiconductor of be disclosed in Jap.P. open Hei7-130652 number, Hei8-78329 number, Hei10-135468 number and Hei10-135469 number.

For constituting active matrix liquid crystal display device, only pixel portion just needs 1,000,000 to 2,000,000 crystal TFT, forms additional functional circuit and then need more crystal TFT around it.The required specification of liquid crystal display device is strict, in order to realize stable liquid crystal display, must guarantee the reliability of each crystal TFT.

The characteristic of TFT can be considered by ON state and OFF state.Some characterisitic parameters such as ON state current, mobility, S value and threshold value all are on-state characteristics, and off-state current then is a most important pass step response.

Yet the off-state current that a problem is arranged is crystal TFT raises easily.

And from the viewpoint of reliability, crystal TFT also is not used in the MOS transistor (making transistor on the crystalline semiconductor substrate) of LSI.For example, degradation phenomena takes place when having observed crystal TFT by continuous drive, wherein mobility and ON state current (electric current that flows through during the TFT ON state) descend, and off-state current (electric current that flows through during the TFT OFF state) rises.Imagining its reason is hot carrier's effect, and promptly near the hot carrier of the high electric field generation drain electrode has caused degradation phenomena.

Know that using lightly doped drain (LDD) structure to alleviate near the high electric field of drain electrode is the method that reduces the MOS transistor off-state current.This structure forms doped regions in the channel region outside, and this doped regions is called the LDD district.

Particularly, its LDD district of a kind of structure is arranged through gate insulating film and gate electrode (the overlapping LDD structure of grid-leakage, GOLD structure), near the high electric field region the drain electrode is weakened, and can prevent hot carrier's effect, thereby improves reliability.Notice that the LDD district is called Lov district (a LDD district) through the zone of gate insulating film and gate electrode in this manual.

Be also noted that some known structures such as LATID (high spud angle injection drain region) structure and ITLDD (transoid T LDD) structure all are the GOLD structures.A kind of GOLD structure is arranged, for example, according to Hatano M., Akimoto H., and Sakai T., IEDM97 Technical Digest, positive.523-6,1997 reports, its sidewall is formed by silicon, has confirmed to compare with other TFT structure to obtain extremely superior reliability.

Note, in this manual, the LDD district not with gate electrode through gate insulating film and overlapping areas is called Loff district (the 2nd LDD district).

Having proposed several method makes and has the two TFT of Loff district and Lov district.A kind of method is only used mask and is not had an autoregistration, and a kind of method is used has the two layer gate electrode of different in width and gate insulating film is self aligned, and these all can be used as the method that forms Lov district and Loff district.

Yet, need be with two masks when forming Lov district and Loff district with mask, operation has also increased.On the other hand, when forming Lov district and Loff district, need not increase the mask number, thereby can reduce operation with autoregistration.Yet the width of gate electrode and the thickness of gate insulating film can influence the Lov district of formation and the position in Loff district.The corrosion rate of gate electrode and gate insulating film often has very big difference, is difficult to accurately control the position alignment in Lov district and Loff district.

In view of above-mentioned, the objective of the invention is when forming Lov district and Loff district, to reduce mask count, also to be easy to form Lov district and Loff district in desirable position.And, the present invention also aims to the crystal TFT that realizes having good ON state and close step response.Another object of the present invention is to realize the semiconductor display device of high reliability, and its semiconductor circuit is made of such crystal TFT.

Utilize the autoregistration of gate electrode and mask in semiconductor layer, to mix impurity and form Lov district and Loff district.Gate electrode is made of two-layer conducting film, and that one deck of more close semiconductor layer (first grid electrode) vertically will be longer than from semiconductor layer layer (second gate electrode) far away along raceway groove.

Notice that in this manual, the vertical speech of raceway groove refers to the direction that charge carrier moves between source region and drain region.

In the present invention, first grid electrode and second gate electrode along raceway groove vertically the length of (charge carrier moving direction) (after this be called for short and make gate electrode width) be different.Carrying out ion with the first grid electrode and second gate electrode as mask injects, because gate electrode thickness difference, utilize the poor of the ion depth of penetration, can make that the ion concentration in the semiconductor layer is lower than under first grid electrode and don't the ion concentration in the semiconductor layer below second gate electrode below second gate electrode.In addition, can also make under first grid electrode and don't the ion concentration in the semiconductor layer below second gate electrode is lower than the not ion concentration of the semiconductor layer below first grid electrode.

And the Loff district forms with mask, therefore need only control the width of the first grid electrode and second gate electrode with corrosion, and the control of Loff district and Lov zone position is just easy than the example of routine.So the TFT that the accurate aligning in Lov district and Loff district and making have desirable characteristics has become easily.

Structure of the present invention is as follows.

According to the present invention, a kind of semiconductor display device is provided, it comprises: the semiconductor layer that forms on insulating surface; The gate insulating film that links to each other with semiconductor layer; The first grid electrode that links to each other with gate insulating film; Second gate electrode that links to each other with first grid electrode; And liquid crystal cell, its characteristics are:

Semiconductor layer has: channel formation region; The LDD district that contacts with channel formation region; And the source region and the drain region that contact with the LDD district;

Along raceway groove longitudinally the width of first grid electrode greater than along the raceway groove width of second gate electrode longitudinally;

The LDD district and first gate electrode, gate insulating film is sandwiched in therebetween;

Liquid crystal cell has: pixel electrode; To electrode; And be formed on pixel electrode and to the liquid crystal between the electrode; And

Source region or drain region are electrically connected with pixel electrode.

Semiconductor layer has: channel formation region; The LDD district that contacts with channel formation region; And the LDD district that contacts with the drain region with the source region;

The channel formation region and second gate electrode, gate insulating film is sandwiched in therebetween;

Source region or drain region are electrically connected with pixel electrode.

According to the present invention, a kind of semiconductor display device is provided, it comprises: the TFT that has semiconductor layer that forms on insulating surface; The gate insulating film that links to each other with semiconductor layer; The first grid electrode that links to each other with gate insulating film; Second gate electrode that links to each other with first grid electrode; And liquid crystal cell, its characteristics are:

The marginal portion of first grid electrode has taper profile;

Source region or drain region are electrically connected with pixel electrode.

Characteristics of the present invention are, do mask autoregistration in semiconductor layer with second gate electrode and mix impurity element and form the LDD district.

Characteristics of the present invention are that a zone is arranged in the LDD district, its impurity concentration gradient is at least 1 * 10¹⁷～1 * 10¹⁸Atom/cm³, and the concentration of LDD district impurity element increases with the increase of distance channel formation region distance.

According to the present invention, a kind of semiconductor display device is provided, it comprises: pixel TFT and driving circuit TFT, each all has the semiconductor layer that forms on insulating surface; The gate insulating film that links to each other with semiconductor layer; The first grid electrode that links to each other with gate insulating film is with second gate electrode that links to each other with first grid electrode; And liquid crystal cell, its characteristics are:

The semiconductor layer of pixel TFT has: with the channel formation region of second gate electrode, gate insulating film is sandwiched in therebetween; The one LDD district contacts with channel formation region, and with first gate electrode, gate insulating film is sandwiched in therebetween; The 2nd LDD district contacts with a LDD district; The source region contacts with the 2nd LDD district with the drain region;

The semiconductor layer of driving circuit TFT has: with the channel formation region of second gate electrode, gate insulating film is sandwiched in therebetween; The 3rd LDD district contacts with channel formation region, and with first gate electrode, gate insulating film is sandwiched in therebetween; Source region or drain region contact with the 3rd LDD district;

The source region of pixel TFT or drain region are electrically connected with pixel electrode.

The marginal portion of first grid electrode has taper profile;

Liquid crystal cell has: pixel electrode; To electrode; And be formed on pixel electrode and to the liquid crystal between the electrode;

Characteristics of the present invention are in a LDD district zone is arranged, and its impurity concentration gradient is at least 1 * 10¹⁷～1 * 10¹⁸Atom/cm³, and the concentration of LDD district impurity element increases with the increase of distance channel formation region distance.

Characteristics of the present invention are in the 3rd LDD district a zone is arranged, and its impurity concentration gradient is at least 1 * 10¹⁷～1 * 10¹⁸Atom/cm³, and the concentration of LDD district impurity element increases with the increase of distance channel formation region distance.

Characteristics of the present invention are, do mask autoregistration in semiconductor layer with second gate electrode and mix impurity and form a LDD district or the 3rd LDD district.

According to the present invention, a kind of semiconductor display device is provided, it comprises: the semiconductor layer that forms on insulating surface; Gate insulating film; First grid electrode; Second gate electrode; First lead-in wire; Second lead-in wire; First interlayer dielectric; Second interlayer dielectric; Middle leads; And liquid crystal cell, its characteristics are:

On insulating surface, form the gate insulating film that covers semiconductor layer;

Make the first grid electrode and first lead-in wire that contact with gate insulating film;

Make respectively and go between with second gate electrode and second that first grid electrode contacts with first lead-in wire;

The first grid electrode and first lead-in wire are made of first conducting film;

Second gate electrode and second lead-in wire are made of second conducting film;

Make first interlayer dielectric, it covers: the first grid electrode and second gate electrode; First lead-in wire and second lead-in wire; And gate insulating film;

On first interlayer dielectric, make second interlayer dielectric;

Make to cover the middle leads of second interlayer dielectric, make it to contact with first interlayer dielectric through the contact hole in second interlayer dielectric, opened;

The middle leads and second lead-in wire are overlapping at the contact hole place, and first interlayer dielectric is sandwiched in therebetween;

The LDD district and first gate electrode, gate insulating film is sandwiched in therebetween.

Source region or drain region are electrically connected with pixel electrode.

On first interlayer dielectric, make second interlayer dielectric;

Make to cover the middle leads of second interlayer dielectric, make it to contact with first interlayer dielectric through first contact hole in second interlayer dielectric, opened;

The middle leads and second lead-in wire are overlapping at the first contact hole place, and first interlayer dielectric is sandwiched in therebetween;

Middle leads links to each other with source region or drain region through second contact hole, and second contact hole is opened in gate insulating film, first interlayer dielectric and second interlayer dielectric;

According to the present invention, a kind of semiconductor display device is provided, it comprises: the semiconductor layer that forms on insulating surface; Gate insulating film; First grid electrode; Second gate electrode; First lead-in wire; Second lead-in wire; First interlayer dielectric; Second interlayer dielectric; Middle leads; Screened film; And liquid crystal cell, its characteristics are:

On first interlayer dielectric, make second interlayer dielectric;

Screened film is to be made by the conducting film identical with middle leads;

On second interlayer dielectric, make screened film, make it overlapping with channel formation region;

Source region or drain region are electrically connected with pixel electrode.

According to the present invention, a kind of semiconductor display device is provided, it comprises: the semiconductor layer that forms on insulating surface; Gate insulating film; First grid electrode; Second gate electrode; First lead-in wire; Second lead-in wire; First interlayer dielectric; Second interlayer dielectric; Middle leads; Screened film;

And liquid crystal cell, its characteristics are:

On first interlayer dielectric, make second interlayer dielectric;

Screened film is to be made by the conducting film identical with middle leads;

Source region or drain region are electrically connected with pixel electrode.

According to the present invention, a kind of semiconductor display device is provided, it comprises: form optical screen film on substrate; On substrate, form the dielectric film that covers optical screen film; On dielectric film, form semiconductor layer; The gate insulating film that contacts with semiconductor layer; The first grid electrode that contacts with gate insulating film; Second gate electrode that contacts with first grid electrode; And liquid crystal cell, its characteristics are:

Optical screen film is through dielectric film and overlapping with channel formation region;

Source region or drain region are electrically connected with pixel electrode.

Characteristics of the present invention are: dielectric film is thrown flat with CMP polishing method.

The present invention can be with use semiconductor display device for gamma camera, the video reproduction equipment of its feature, wear display device or personal computer.

According to the present invention, a kind of method of making semiconductor display device is provided, may further comprise the steps:

On insulating surface, form semiconductor layer;

Making gate insulating film makes it to contact with semiconductor layer;

Making first conducting film makes it to contact with gate insulating film;

Making second conducting film makes it to contact with first conducting film;

First conducting film and the second conducting film needle drawing shape are made the first grid electrode and second gate electrode;

The first grid electrode and second gate electrode with semiconductor layer mix first impurity to semiconductor layer;

On semiconductor layer, form to cover the mask of the first grid electrode and second gate electrode, and in semiconductor layer, by means of mixing conduction type second impurity identical and make: channel formation region with first impurity from being formed on mask on the semiconductor layer; A LDD district that contacts with channel formation region; The 2nd LDD district that contacts with a LDD district; And the source region and the drain region that contact with the 2nd LDD district;

The interlayer dielectric that making is made up of single or multiple lift, it covers semiconductor layer, first grid electrode and second gate electrode;

Opening contact hole in interlayer dielectric;

Make pixel electrode, it links to each other with source region or drain region through contact hole, and its characteristics are:

First grid electrode is along longer than second gate electrode on the raceway groove longitudinal direction;

The one LDD district and first gate electrode, gate insulating film is sandwiched in therebetween.

On insulating surface, form semiconductor layer;

Making gate insulating film makes it to contact with semiconductor layer;

Making first conducting film makes it to contact with gate insulating film;

Making second conducting film makes it to contact with first conducting film;

Mix first impurity from the first grid electrode and second gate electrode of semiconductor layer to semiconductor layer;

Opening contact hole in interlayer dielectric;

On insulating surface, form semiconductor layer;

Making gate insulating film makes it to contact with semiconductor layer;

Make first shape, first conductive layer and make it to contact, and make first shape, second conductive layer with gate insulating film;

Corrode first shape, first conductive layer and first shape, second conductive layer, form first grid electrode with tapering part and second gate electrode with tapering part;

Mix the impurity element that is single conduction type through gate insulating film to semiconductor layer, form the 2nd LDD district; Simultaneously, the tapering part of process first grid electrode mixes the impurity element that is single conduction type to semiconductor layer, forms a LDD district, and impurity concentration wherein increases to the marginal portion of semiconductor layer;

Tapering part with first and second gate electrodes mixes the impurity element that is single conduction type as mask, forms source region or drain region;

Make the interlayer dielectric of single or multiple lift, it covers: semiconductor layer; First grid electrode; And second gate electrode;

Opening contact hole in interlayer dielectric;

The pixel electrode that making contacts with source region or drain region through contact hole.

On insulating surface, form semiconductor layer;

Making gate insulating film makes it to contact with semiconductor layer;

Making first conducting film makes it to contact with gate insulating film;

Making second conducting film makes it to contact with first conducting film;

Corrode second conducting film, make first shape, second conductive layer;

Corrode first conducting film, make first shape, first conductive layer;

Opening contact hole in interlayer dielectric;

In the accompanying drawings:

Figure 1A～1F is a process drawing of making liquid crystal display device of the present invention;

Fig. 2 A and 2B are the enlarged drawings of TFT gate electrode;

Fig. 3 A～3D is a process drawing of making liquid crystal display device of the present invention;

Fig. 4 A-4D represents to make the process drawing of liquid crystal display device of the present invention;

Fig. 5 A and 5B represent to make the process drawing of liquid crystal display device of the present invention;

Fig. 6 is a process drawing of making liquid crystal display device of the present invention;

Fig. 7 A and 7B are respectively the vertical view and the circuit diagram of liquid crystal display device pixel of the present invention;

Fig. 8 is the sectional view of liquid crystal display device of the present invention;

Fig. 9 is the sectional view of liquid crystal display device of the present invention;

Figure 10 is the sectional view of liquid crystal display device of the present invention;

Figure 11 is the sectional view of liquid crystal display device of the present invention;

Figure 12 A and 12B are respectively the vertical view and the sectional view of liquid crystal display device pixel of the present invention;

Figure 13 A and 13B represent the method for crystallization semiconductor layer;

Figure 14 A and 14B represent the method for crystallization semiconductor layer;

Figure 15 A and 15B represent the method for crystallization semiconductor layer;

Figure 16 is the block scheme of liquid crystal display device of the present invention;

Figure 17 A～17F is to use the electronics equipment of liquid crystal display device of the present invention;

Figure 18 A～18D is a process drawing of making liquid crystal display device of the present invention;

Figure 19 A and 19B are the enlarged drawings of TFT gate electrode;

Figure 20 represents for shape A, the thickness of TaN and the relation of electron temperature;

Figure 21 represents for shape B, the thickness of TaN and the relation of electron temperature;

Figure 22 is for shape B, the comparison of electron temperature and horizontal direction electric field intensity;

Figure 23 is illustrated in the CONCENTRATION DISTRIBUTION of phosphorus among shape A and the B.

The model embodiment

Figure 1A～1F represents structure of thin film transistor (TFT) of the present invention and preparation method thereof.

Onsubstrate 100, form basement membrane 101.Not necessarily to formbasement membrane 101, but have it can prevent that the impurity ofsubstrate 100 from spreading to semiconductor layer.The crystalline semiconductor film of being made by known method forms

semiconductor layer

102 and 103 onbasement membrane 101.

Make thegate insulating film 104 that coverssemiconductor layer 102 and 103.Ongate insulating film 104, makefirst conducting film 105 andsecond conducting film 106 then, to constitute gate electrode.Notice that first conductingfilm 105 andsecond conducting film 106 must be to have to corrode optionally conductive material (seeing Figure 1A).

Then on

semiconductor layer

102 and 103,form Etching mask 107 and 108.Form the first shape conductive layer 109 and 110 (firstconductive layer 109a and the 110a, and secondconductive layer 109b and the 110b) (seeing Figure 1B) with

mask

107 and 108 corrosion first conductingfilms 105 and second conducting films 106 (first corrosion process) then.

Fig. 2 A is the first shape conductive layer 109 of Figure 1B and 110 enlarged drawing.The marginal portion of the first

conductive layer

109a and 110a, the marginal portion that reaches the second

conductive layer

109b and 110b has all become taper, shown in Fig. 2 A.And then corrosiongate insulating film 104, make not by the first shape conductive layer 109 and the 110 regional attenuates that cover, become the first shapegate insulating film 104a.

Next carry out second corrosion process, shown in Fig. 1 C.Anisotropic etch first shape, the secondconductive layer 109b and the 110b and firstconductive layer 109a and the 110a, but the latter's corrosion rate is slower than the former, thereby form the second shape conductive layer 113 and 114 (first conductive layer 113a and the 114a, and second conductive layer 113b and the 114b).

The second shape conductive layer 113 of Fig. 1 C and 114 enlarged drawing are shown in Fig. 2 B.Corrosion to the second conductive layer 113b and 114b in second corrosion process will be more than first conductive layer 113a and the 114a, shown in Fig. 2 B.And then in second corrosion process,

mask

107 and 108 is corroded into mask 111 and 112.Corrode the first shapegate insulating film 104a again, not making is become the second shape gate insulating film 104b by the regional attenuates of the second shape conductive layer 113 and 114 coverings.

Remove mask 111 and 112, and in

semiconductor layer

102 and 103, carry out the first step and mix, mix n type conductive impurity element, shown in Fig. 1 D.During doping with the second shape conductive layer 113 and 114 as mask to stop impurity element.And the zone that the doping of finishing makes it below the second shape conductive layer 113a and 114a has also added impurity element.

So just formed with overlapping first impurity range 115 of the first conductive layer 113a and 114a and 116 and impurity concentration be higher than second impurity range 117 and 118 of first impurity range.Note,, the invention is not restricted to this though mix n type impurity after in this model embodiment, removing mask 111 and 112.In the technological process of Fig. 1 D, also can after mixing n type conductive impurity element, remove mask 111 and 112 again.

Onsemiconductor layer 103,form mask 119 to cover the second shape conductive layer 114 with resist.The part of themask 119 and second impurity range 118 is overlapping, and the second shape gate insulating film 104b is sandwiched in therebetween.Carried out for second step then and mix, mix n type impurity element.It is to carry out under such condition that the n type mixes, and promptly dosage mixes than the first step and increases and the accelerating potential reduction.Exceptchannel formation region 124 andLov district 123, in the doping of second step,source region 120,drain region 121 andLoff district 122 insemiconductor layer 103, have also been formed in self aligned mode.In the doping of second step, make mask, also formed the 3rd impurity range 125 (seeing Fig. 1 E) with second shape, the first conductive layer 113a.

Control the size ofmask 119 in the present invention, the size inLoff district 122 can freely be set.

On all surfaces of thesemiconductor layer 103 that forms the n channel TFT, cover Etching mask 126 then, shown in Fig. 1 F.Make mask to stop that impurity element is entrained in source region 127, drain region 128 and Lov district 129 by the 3rd step and mixes the impurity element that is p type conduction with the second shape conductive layer 113; In thesemiconductor layer 102 of making the p channel TFT, just made channel formation region 130 in self aligned mode.

The n type impurity of variable concentrations has mixed source region 127, drain region 128 and Lov district 129, but in the p type impurity concentration of mixing during far above n type impurity, the conduction type in source region 127, drain region 128 and Lov district 129 just becomes the p type.

In

semiconductor layer

102 and 103, made impurity range (source region, drain region, Lov district and Loff district) by above-mentioned technological process.With

semiconductor layer

102 and 103 overlapping second shape conductive layers 113 and 114 as gate electrode.Second shape, first conductive layer 113a and 114a are called first grid electrode, and second shape, second conductive layer 113b and 114b are called second gate electrode.

Then activation is mixed the impurity of each semiconductor layer with control electric conductivity.Yet, if first conductingfilm 105 and the used heat labile words of conductive material ofsecond conducting film 106 are preferably in and activate after forming interlayer dielectric (contain silicon and be its principal ingredient) again, with the protection some parts as lead-in wire.

In addition, in the atmosphere that contains 3-100% hydrogen, heat-treat the hydrogenation that can realizesemiconductor layer 102 and 103.This process is with the outstanding key in the next saturated semiconductor layer of heat activated hydrogen.Plasma hydrogenization (with the hydrogen of plasma activation) also can be used as another kind of hydrogenation means.

When above-mentioned technological process finishes, p channel TFT 141 and n channel TFT 142 have just been finished.

Note, though each surface shown in Figure 1A～1F and Fig. 2 A and Fig. 2 B all is flat, for raceway groove vertically on the second shape first grid electrode 113a and 114a than the zone that the second gate electrode 113b and 114b grow, be actually tapering, exist minimum cone angle.Be also noted that, depend on etching condition, also may make flat.

As mentioned above, first grid electrode and second gate electrode along raceway groove vertically the length (after this being called for short gate electrode width) of (charge carrier moving direction) be different in the present invention.Carry out ion when injecting with first grid electrode and second gate electrode as mask, utilizing the difference of the ion depth of penetration that the difference because of gate electrode thickness produces.Therefore just can make that the ion concentration in the semiconductor layer is lower than below first grid electrode and don't the ion concentration of the semiconductor layer under second gate electrode below second gate electrode.In addition, also can make below first grid electrode and don't the ion concentration of the semiconductor layer under second gate electrode is lower than the not ion concentration of the semiconductor layer below first grid electrode.

Moreover, in order to form the Loff district, only needing width by the corrosion control first grid electrode and second gate electrode with mask, the position of therefore controlling Loff district and Lov district is just easy than the example of routine.So just accomplish the accurate location aligning in Lov district and Loff district easily, it is also just easy to make the TFT with desirable characteristics.

Embodiment

Embodiments more of the present invention are described as follows.

[embodiment 1]

Describe the method for on same substrate, making pixel portion simultaneously and being formed on pixel portion driving circuit TFT (n raceway groove and p channel TFT) on every side in theembodiment 1 in detail.

At first, as shown in Figure 3A, onsubstrate 300, form by dielectric film, as silicon dioxide film, silicon nitride film or silicon oxynitride film, the basement membrane of making 301, substrate is made by glass or quartz, as borosilicic acid barium or alumina borosilicate glass, typically as the #7059 or the #1737 glass of Corning Incorporated (CorningCorp.).For example, use plasma CVD method by SiH₄, NH₃And N₂The silicon oxynitride film that O makes, and thickness 10～200nm (best 50～100nm), similarly by SiH₄And N₂It is the hydrogenated silicon oxynitride film of 50～200nm (being preferably between 100～150nm) that O makes thick, and forms lamination.Notice that thebasement membrane 301 of double-layer structure is represented as one deck in Fig. 3 A.Notice that shown in theembodiment 1 is thatbasement membrane 301 is the example of double-layer structure, but also can form the rhythmo structure that the individual layer of one of above-mentioned dielectric film or three layers or multilayer build up.

Semiconductor layer 302～304th is made of the crystalline semiconductor film, is that the semiconductor film with impalpable structure carries out laser crystallization, or make of known thermal crystallisation method.The thickness ofsemiconductor layer 302～304 is 25～80nm (being preferably between 30～60nm).Material to the crystalline semiconductor film does not have assorted petty restriction, but is preferably made by semiconductor material such as silicon or germanium-silicon alloy (SiGe).

As for known crystallization method, have the thermal crystallisation method of using electric furnace, with the laser annealing crystallization method of laser, with the lamp of infrared lamp according to annealing crystallization method, and with the crystallization method of catalytic metal.

Excimer laser, YAG laser instrument and the YVO of pulse emission or continuous emission type₄Laser instrument all can be used as lasing light emitter and is used for the laser crystallization legal system and makes the crystalline semiconductor film.With such laser instrument the time, can use light to gather into wire through optical system with the laser instrument emission, shine the method on the semiconductor film again.The operator can suitably select crystallization condition, but when using excimer laser, the frequency of pulse emission is 30Hz, and laser energy density is 100～400mJ/cm²(typically at 200～300mJ/cm²Between).In addition, utilize its second harmonic when using the YAG laser instrument, the pulse transmission frequency is 1～10KHz, and laser energy density can be 300～600mJ/cm²(typically at 350～500mJ/cm²Between).The laser that gathers into wire, wide 100～1000 μ m, 400 μ m for example shine the whole surface of substrate then.For the laser of wire, this is that overlap ratio (overlap ratio) with 80～98% is carried out.

Makegate insulating film 305, cover on thesemiconductor layer 302～304.Thick is siliceousgate insulating film 305 usefulness plasma CVDs or the sputtering method making of 40～150nm.In embodiment 1, made the thick silicon oxynitride film of 120nm.Certainly, gate insulating film is not limited to this silicon oxynitride film, the containing silicon insulating film and also can use of other individual layers or rhythmo structure.For example, when using silicon oxide film, available plasma CVD method makes TEOS (tetraethyl orthosilicate) and O₂Potpourri under the reaction pressure of 40Pa, underlayer temperature is 300～400 ℃, at 0.5～0.8W/cm²High frequency (13.56MHz) electrical power density under discharge form silicon oxide film.The silicon oxide film of Zhi Zuoing then carries out thermal annealing under 400～500 ℃ like this, can obtain the gate insulating film of superperformance.

Ongate insulating film 305, makefirst conducting film 306 andsecond conducting film 307 then to formgate electrode.In embodiment 1,first conducting film 306 is to be made by the thick Ta of 50～100nm (tantalum), and second conductingfilm 307 is to be made by the thick W of 100～300nm (tungsten).

The Ta film is made of sputtering method, with Ar sputter Ta target.If when sputter, in Ar, add an amount of Xe and Kr, can eliminate the internal stress of Ta film, thereby prevent peeling off of film.The Ta film resistance rate of α phase is 20 μ Ω cm, can be used as gate electrode, but the Ta film resistance rate of β phase is 180 μ Ω cm, is unsuitable for doing gate electrode.Crystal structure forms α phase Ta film near the tantalum nitride of α phase Ta as the substrate of Ta if form thick 10～50nm, and the Ta film of α phase can easily obtain.

The W film is done the target sputter with W and is formed.The also available hot CVD method of W film is by tungsten hexafluoride (WF₆) make.No matter use any method, film must be made low-resistance with use as gate electrode, preferably make the W film resistance rate of making be equal to or less than 20 μ Ω cm.The crystal grain that increases the W film can reduce resistivity, but the situation of many impurity elements such as oxygen is arranged in the W film, can hinder crystallization, and film becomes high resistant.Therefore purity is that 99.9999% or 99.99% W target is used for sputter.In addition, if when forming the W film, pay special attention to from gas phase, not introduce impurity, the resistivity that then can accomplish 9-20 μ Ω cm.

Notice that though inembodiment 1, the material offirst conducting film 306 is Ta, the material ofsecond conducting film 307 is W, and conducting film is not limited to these, corrodes optionally that conductive material gets final product so long as have.First conductingfilm 306 andsecond conducting film 307 also can be by being selected from a kind of in this group element of Ta, W, Ti, Mo, Al and Cu, or are the alloy material of principal ingredient with one of these elements, or made by the compound of these elements.And, also can use semiconductor film, typically be polysilicon film, be mixed with impurity element in the film, asphosphorus.In embodiment 1 employee, the preferred examples combination also comprises: first conducting film of being made by tantalum nitride (TaN) and second conducting film of being made by W; First conducting film of making by tantalum nitride (TaN) and second conducting film of making by Al; First conducting film of making by tantalum nitride (TaN) and second conducting film of making by Cu (seeing Fig. 3 B).

Then, formmask 308～311, carry out first corrosion process to make electrode and lead-in wire byresist.In embodiment 1, use ICP (inductively coupled plasma) etch.CF₄And Cl₂Mixed gas as etchant gas, and the radio-frequency power (13.56MHz) that under the pressure of 1Pa the electrode of coiled type is applied 500W produces plasma.Substrate side (sample stage) also applies the radio-frequency power (13.56MHz) of 100W, applies negative self-bias effectively.At CF₄And Cl₂When share, W film and Ta film all are corroded with same magnitude.

Note, though not shown among Fig. 3 C, under above-mentioned etching condition, use the Etching mask of suitable shape, according to the added bias voltage of substrate side, the marginal portion of first conductive layer and second conductive layer is made into taper.The angle of tapering part is 15 °～45 °.Etching time can increase 10-20%, so that the corrosion back does not have residue on gate insulating film.Silicon oxynitride film is 2～4 (typically being 3) to the selection ratio of W film, and therefore the silicon nitride film that has 20～50nm to expose approximately in this excessive erosion process is corroded.In addition, though not shown in Fig. 3 C,gate insulating film 305 is not thinned 20～50nm by the zone that the first shape conductive layer 312-315 covers yet, and has formed the first shapegate insulating film 305a.

So, in first corrosion process, formed the first shapeconductive layer 312～315 (the firstconductive layer 312a～315a and the secondconductive layer 312b～315b) by first conductive layer and second conductive layer.

Next carry out second corrosion process, shown in Fig. 3 D.Similarly use the ICP etch, use CF₄, Cl₂And O₂Potpourri as etchant gas, the radio-frequency power (13.56MHz) that applies 500W to the electrode of coiled type under the pressure of 1Pa produces plasma.The radio frequency of 50W (13.56MHz) power is added to substrate side (sample stage), and applies the self-bias lower than first corrosion process.Under these etching conditions, the W film is by anisotropic etch, and Ta film (first conductive layer) with slower speed by anisotropic etch, form the second shapeconductive layer 320～323 (the firstconductive layer 320a～323a and the secondconductive layer 320b～323b).In addition, though not shown among Fig. 3 D, the zone thatgate insulating film 305 is not covered by the second shapeconductive layer 320～323 20～50nm that is corroded again becomes thinner, forms the second shape gate insulatingfilm 305b.Mask 308～311 is corroded in second corrosion process, becomesmask 316～319.

According to mixed gas CF₄And Cl₂, the corrosion reaction of W film and Ta film can be estimated by the ionic type and the vapour pressure of group that is produced and reaction product.The fluoride and the muriatic vapour pressure that compare W and Ta, the fluoride WF of W₆Vapour pressure is high, WCl₅, TaF₅And TaCl₅Vapour pressure then have similar magnitude.Therefore W film and Ta film are all by CF₄And Cl₂Gaseous mixture corrosion.Yet, if in this gaseous mixture, add an amount of O₂, CF₄With O₂Reaction generates CO and F, and produces a large amount of F groups and F ion.As a result, the W erosion speed with high fluoride vapour pressure increases.On the other hand, even F increases, the corrosion rate of Ta does not increase relatively yet.In addition, therefore Ta adds O than the easy oxidation of W₂Back Ta's is surperficial oxidized.The corrosion rate of Ta film can further reduce, because the oxide of Ta does not react with fluoride and chloride.Therefore can make the corrosion rate of W film and Ta film that difference is arranged, and the corrosion rate that makes the W film is greater than the Ta film.

Removemask 316～319, carry out the first doping process shown in Fig. 4 A, mix the impurity that is n type conduction.For example, can be at the accelerating potential and 1 * 101 of 70-120keV³Atom/cm²Dosage under mix.Mix as mask with secondconductive layer 320b～322b, make impurity mix zone below firstconductive layer 320a～322a.Like this, just formed first impurity range 325～327 overlapping, and impurity concentration is higher than second impurity range 328～330 of first impurity range with firstconductive layer 320a～322a.Note, inembodiment 1, removing and carrying out the n type behind themask 316～319 and mix, but the invention is not restricted to this.Also can in the step of Fig. 4 A, carry out the n type and mix, removemask 316～319 then.

Next onsemiconductor layer 304, make mask 331 and cover second conductive layer 318.The part of mask 331 and second impurity range 330 are overlapping, and the second shapegate insulating film 305b is sandwiched in therebetween.Carry out the second doping process then, mix n type impurity.Be higher than at dosage and carry out n type mix (seeing Fig. 4 B) under the condition of the first doping process and low accelerating potential.Available ion doping or ion inject and mix.Ion doping is 1 * 10¹³～5 * 10¹⁴Atom/cm²Dosage and the accelerating potential of 60～100keV under carry out.V group element in the periodic table, typically phosphorus (P) or arsenic (As) are used as n type impurity, and used herein is phosphorus (P).In the case, the second shape

conductive layer

320 and 321 becomes the mask of n type impurity, and forms source region 332～334, drain region 335～337, mesozone 338 and Lov district 339 and 340 with self-aligned manner.In addition, form Loff district 341 by mask 331.The concentration of mixing the n type impurity in source region 332～334 and drain region 335～337 is 1 * 10²⁰-1 * 10²¹Atom/cm³Scope.

According to the present invention, the size of control mask 331 can freely be provided with along the length in Loff district 341 on the charge carrier moving direction.

Mix n type impurity element, make in the Loff district andform 1 * 10¹⁷～1 * 10¹⁸Atom/cm³Withform 1 * 10 in the Lov district¹⁶～3 * 10¹⁸Atom/cm³Impurity concentration.

Note, in Fig. 4 B, also can before or after make mask on thesemiconductor layer 304, under 70～120keV accelerating potential, carry out the n type and mix.Above-mentioned technological process reduces the n type impurity concentration that becomes the Loff of pixel TFT district 341 parts, and the n type impurity concentration of Lov district 340 parts of the n channel TFT that driving circuit uses is raise.The n type impurity concentration that suppresses to become Loff district 341 parts of pixel TFT can reduce the off-state current of pixel TFT.And the n type impurity concentration of Lov district 340 parts of the n channel TFT that the rising driving circuit is used can prevent because of near the high electric field drain region produces hot carrier, the degradation phenomena that causes owing to hot carrier's effect.The n type impurity concentration of Lov district 340 parts of the n channel TFT of using at driving circuit is preferably 5 * 10¹⁷～5 * 10¹⁹Atom/cm³

Then in thesemiconductor layer 302 that forms the p channel TFT, mix the impurity element with above-mentioned single conductivity type opposite, form source region 360, drain region 361 and Lov district 342, shown in Fig. 4 C.The second shapeconductive layer 320 forms impurity range as the impurity mask with self-aligned manner.At this moment cover with Etching mask 343 on thesemiconductor layer 303 of making n channel TFT and 304 the whole surface.The phosphorus of variable concentrations has mixed source region 360, drain region 361 and Lov district 342, uses diborane (B here₂H₆) carry out ion doping, make the concentration of each regional boron-doping reach 2 * 10²⁰～2 * 10²¹Atom/cm³In fact, source region 360, drain region 361 and Lov district 342 contained boron concentration are subjected to the influence of conductive layer and insulator film thickness, and with the second doping similar process, the section at conductive layer and dielectric film edge partly has tapering on semiconductor layer.So the concentration of the impurity element that mixes also changes.

In eachsemiconductor layer 302～304, formed impurity range (source region, drain region, Lov district and Loff district) by above-mentioned technological process.With the overlapping second shapeconductive layer 320～322 ofsemiconductor layer 302～304 as gate electrode.In addition, the second shapeconductive layer 323 is as the electric capacity lead-in wire.

The impurity that each semiconductor layer is mixed activates then, with the control conduction type.Carry out this technological process with annealing furnace as thermal annealing.In addition, also can use laser annealing and rapid thermal annealing (RTA).Thermal annealing is to be equal to or less than in the blanket of nitrogen of 1ppm at oxygen concentration, preferably is equal to or less than 0.1ppm, at 400～700 ℃, typically carries out between 500～600 ℃.Thermal treatment is to carry out under 500 ℃ 4 hours in embodiment 1.Yet,, be preferably in and make interlayer dielectric (principal ingredient is a silicon) and activate afterwards, with grill-protected electrode and lead-in wire etc. for firstconductive layer 306 and the used heat labile situation of conductive material of secondconductive layer 307.

In addition, in the atmosphere that contains 3～100% hydrogen, came in 1～12 hour the island semiconductor layer is carried outhydrogenation 300～450 ℃ of following thermal treatments.This process is to make the outstanding key in the island semiconductor layer saturated with heat activated hydrogen.Also available plasma hydrogenization (with the hydrogen of plasma activation) is as another kind of hydrogenation means.

Next step, with thick be that the silicon oxynitride film of 100～200nm is made first interlayer dielectric 344.Onfirst interlayer dielectric 344, makesecond interlayer dielectric 345 then with organic insulation.

Opening contact hole insecond interlayer dielectric 345 on electric capacity lead-inwire 323 exposes a part offirst interlayer dielectric 344 then.Make middle leads 346, it contacts (seeing Fig. 4 D) through the contact hole above the electric capacity lead-inwire 323 withfirst interlayer dielectric 344.

Next step makes the3rd interlayer dielectric 347 by organic insulation onsecond interlayer dielectric 345.

Opening contact hole in the second shapegate insulating film 305b,first interlayer dielectric 344 andsecond interlayer dielectric 345 then, and makesource electrode line 348～350 makes it through contact hole and source region 360,333 and contacts with 334.In addition, make the drain lead 351 (seeing Fig. 5 A) that contacts with drain region 361,336simultaneously.Drain line 352 links up drain region 337 and middle leads 346.

Between electric capacity lead-inwire 323 and middle leads 346 and the part that contacts with them, formed storage capacitor atfirst interlayer dielectric 344.

Next step makes the 4th interlayer dielectric 353 by organic resin.Organic resin such as polyimide, polyamide, acrylic resin and BCB (ring benzene butylene) can use.Especially preferably using to have the acrylic resin of superior flatness, mainly is in order to compensate the flatness on surface because form the 4th interlayer dielectric 353.The acrylic resin film of making inembodiment 1, its thickness can fully be filled and led up the step that TFT forms.The thickness of film is preferably in 1～5 μ m (better between 2～4 μ m).

Next step, making reaches the contact hole of middle leads 352 in the4th interlayer dielectric 353, and makes pixel electrode 354.Make the thick tin indium oxide of 110nm (ITO) film inembodiment 1, needle drawing shape is madepixel electrode 354 then.In addition, also can use the potpourri of 2～20% zinc paste and indium oxide as nesa coating.Pixel electrode 354 just becomes the pixel electrode (seeing Fig. 5 B) of liquid crystal cell.

Next step makes alignment films 355, as shown in Figure 6 on the active matrix substrate under Fig. 5 B state.Polyimide resin is used as the alignment films of liquid crystal display cells usually.After making alignment films, wipe processing, make liquid crystal molecule have fixing tilt angle.And, though Fig. 6 is not shown, can between to substrate (opposing substrate) and active matrix substrate, be provided with at interval.

On the other hand, make electrode 357 and alignment films 358 at the back side substrate 356.Though Fig. 6 is not shown, also screened film can be arranged to substrate 356.In this case, thick is that the screened film of 150～300nm can be made by Ti film, Cr film or Al film.Then the active matrix substrate that will be formed with pixel portion and driving circuit with the sealant (not shown) with substrate is coupled together.The filling agent (not shown) is sneaked into sealant, keep a uniform gap according to filling agent (or at interval, depending on the circumstances) between two substrates.Between two substrates, inject liquid crystal material 359 then.Can use known liquid crystal material.For example, except the TN liquid crystal, can use the antiferroelectric mixed liquid crystal of no threshold value with photoelectric response characteristic, its transmissivity continuously changes with electric field.The V-shaped photoelectric response characteristic of the antiferroelectric mixed liquid crystal of some no threshold values is also arranged.Like this, just finished active matrix liquid crystal display device shown in Figure 6.

Inembodiment 1,source region 404,drain region 405, Loff district 406, Lov district 407,channel formation region 408 and mesozone 409 are included in the semiconductor layer of pixel TFT 401.Form Loff district 406, make it overlapping without the second shapegate insulating film 305b and gate electrode 318.Make it overlapping but form the Lov407 district through the second shapegate insulating film 305b and gate electrode 318.This structure is extremely effective to reducing the off-state current that causes because of hot carrier's effect.

In addition, pixel TFT 401 is used double-gate structure inembodiment 1, but pixel TFT also can be used single grid structure or multi-gate structure in the present invention.The TFT of two double-gate structures can be together in series effectively, thereby further reduces off-state current.

In addition, pixel TFT 401 is the n channel TFT inembodiment 1, but also can use the p channel TFT.

Note, the active matrix substrate ofembodiment 1, because of all arranging the TFT of preferred structure in pixel portion and driving circuit section, so show high reliability, performance also has improvement.

At first, constitute the used n channel TFT 403 of cmos circuit of driving circuit, have and reduce the structure that operating rate is injected and don't reduced to hot carrier.Notice that so-called driving circuit comprises some circuit so here, as shift register, impact damper, level phase shifter (levelshifter) and sample circuit (sampling and holding circuit).When carrying out digital drive, also can comprise signaling conversion circuit, as the D/A change-over circuit.

Inembodiment 1, the semiconductor layer of the n channel TFT 403 of cmos circuit (driving circuit n channel TFT) comprisessource region 421,drain region 422, Lov district 423 and channel formation region 424.

The semiconductor layer of driving circuit p channel TFT 402 comprisessource region 410,drain region 411, Lov district 412 and channel formation region 413.Form Lov district 412, make it through the second shapegate insulating film 305b and overlapping with gate electrode 320.Notice that driving circuit p channel TFT 402 does not have the Loff district inembodiment 1, but can use the structure in Loff district yet.

Raceway groove of the present invention gate electrode length (after this abbreviating gate electrode width as) longitudinally is different.Therefore, when carrying out the ion injection as mask with gate electrode, the ion depth of penetration differences that utilization causes because of gate electrode thickness is different can make the ion concentration in the semiconductor layer below the first grid electrode be lower than not to be arranged in the ion concentration in the semiconductor layer below the first grid electrode.

In addition, the Loff district forms with mask, therefore need only control the width of the first grid electrode and second gate electrode with corrosion.Compare with the example of routine, the position in control Loff district and Lov district has become easily.Therefore, TFT with desirable characteristics of the accurate location in Lov district and Loff district and making has also just become easily.

In addition, in conventional example, must corrode gate insulating film and first interlayer dielectric comes opening contact hole,, therefore be difficult to form storage capacitor by drain lead, electric capacity lead-in wire and first interlayer dielectric to make the drain lead that connects the pixel TFT drain region.Yet, the present invention makes middle leads at second interlayer dielectric and the intermembranous new system of the 3rd layer insulation, therefore, can form storage capacitor by the middle leads 352,first interlayer dielectric 344 that connect the pixel TFT drain lead and the electric capacity lead-in wire of making simultaneously 323 as the signal line.

Note, though inembodiment 1 explanation be transmission-type liquid crystal display device, the invention is not restricted to this, also can make reflective type liquid crystal display device.In addition, explanation is the situation that pixel TFT is used the n channel TFT inembodiment 1, but the invention is not restricted to this, also can use the p channel TFT as pixel TFT.

And explanation is inembodiment 1, the two situation that all forms of Lov district and Loff district in pixel TFT, but also can use pixel TFT to have only the structure in Lov district.In addition, the structure that only forms the Lov district in driving circuit TFT has been described inembodiment 1, but also can have used Lov district and the two structure that all forms of Loff district in driving circuit TFT.

[embodiment 2]

The upper surface figure of liquid crystal display device pixel portion of the present invention has been described in embodiment 2.

The upper surface of the liquid crystal display device of embodiment 2 is illustrated in Fig. 7 A.And the circuit diagram of the liquid crystal display device pixel portion of embodiment 2 is shown in Fig. 7B.Reference number 501 is represented the source signal line, andreference number 502 is represented the signal line.The lead-in wire of making onsource signal line 501 503 is electric capacity lead-in wires, and it andsource signal line 501 are overlapping.

Reference number 504 represent pixel TFT, pixel TFT has semiconductor layer 505.That part ofsignal line 502 that forms onsemiconductor layer 505 is as gate electrode.The source region ofsemiconductor layer 505 links to each other withsource signal line 501 with one of drain region, and another of source region and drain region utilizesdrain line 510 to link to each other with middle leads 511.That part of electric capacity lead-inwire 503 byreference number 512 representatives is connected to the first interlayer dielectric (not shown), and electric capacity lead-inwire 503, first interlayer dielectric and middle leads 511 are at that part of storage capacitor that then forms ofreference number 512 representatives.

Drain lead 510 links to each other withpixel electrode 509.

Note, embodiment 2 andembodiment 1 at random can be combined.

[embodiment 3]

Except being formed the structure of storage capacitor by electric capacity lead-in wire, first interlayer dielectric and middle leads, embodiment 3 expressions are formed the example of storage capacitor by electric capacity lead-in wire, gate insulating film and semiconductor layer.Note, used with in the identical reference symbol of part shown in Fig. 3 A～6.

Fig. 8 represents the sectional view of the liquid crystal display device of embodiment 3.The liquid crystal display device of embodiment 3 is different from Fig. 5 B those shown, and it has semiconductor layer 600.Other structures are described in embodiment 1.Therefore, the detailed structure about the liquid crystal display device of embodiment 3 can be omitted here referring toembodiment 1.

Semiconductor layer 600 and first electric capacity lead-inwire 323a and second electric capacity lead-inwire 323b are overlapping, and the second shapegate insulating film 305b is sandwiched in therebetween.Second impurity range 601 thatsemiconductor layer 600 haschannel formation region 603,first impurity range 602 that contacts withchannel formation region 603 marginal portions and contacts with first impurity range 602.Impurity concentration infirst impurity range 602 is lower than the impurity concentration in second impurity range 601.In addition,first impurity range 602 and first electric capacity lead-inwire 323a are overlapping, and the second shapegate insulating film 305b is sandwiched in therebetween.

Note, form raceway groove thereby on electric capacity lead-inwire 323, always apply in thechannel formation region 603 of a voltage atsemiconductor layer 600.

Middle leads 346 is linked to each other with thedrain region 405 of pixel TFT 201 by drain line 352.Andfirst interlayer dielectric 344 on the contact hole that middle leads 346 is opened insecond interlayer dielectric 345 and second electric capacity lead-inwire 323b contacts.

Capacitance according to the structure storage capacitor of embodiment 3 can increase.Note, if the surface area of storage capacitor increases, because the aperture is than descending the brightness deterioration of liquid crystal display device.Yet, structure with embodiment 3, by electric capacity lead-inwire 323, second shapegate insulating film 305b andsemiconductor layer 600 storage capacitor that forms and the 323 storage capacitor overlaids that form that gone between bymiddle leads 346,first interlayer dielectric 344 and electric capacity, so the capacitance of storage capacitor can raise and not reduce the aperture ratio.

Note,, the invention is not restricted to this, also can use the p channel TFT as pixel TFT though the example of explanation is that pixel TFT is the n channel TFT in embodiment 3.

Note, can combine withembodiment 1 or 2 as replenishing to embodiment 3.

[embodiment 4]

The example that forms power lead and screened film (black matrix) simultaneously has been described in the embodiment 4.Note, used and the identical reference symbol of part shown in Fig. 3 A～6.

Fig. 9 represents the sectional view of the liquid crystal display device of embodiment 4.The liquid crystal display device of embodiment 4 is different from Fig. 5 B those shown, and it has screened film 701.Notice that other structures are described in embodiment 1.Therefore, the detailed structure of the liquid crystal display device of embodiment 4 can be omitted here referring toembodiment 1.

Middle leads 346 contacts withfirst interlayer dielectric 344 on going between 323b at second electric capacity through the contact hole opened insecond interlayer dielectric 345.

Onsecond interlayer dielectric 345, form screenedfilm 701 simultaneously with middle leads 346.Form the increase that screenedfilm 701 can prevent to cause because of the channel formation region that the light of liquid crystal display device outside is injected pixel TFT off-state current.

In addition, can form the screenedfilm 701 of embodiment 4 simultaneously, therefore, need not to increase process number with middle leads 346.

Note, it is important that in embodiment 4 screenedfilm 701 and middle leads 346 all are to be made by the material that is difficult for printing opacity.

Though explanation is that pixel TFT is the example of n channel TFT in embodiment 4, the invention is not restricted to this, the p channel TFT also can be used as pixel TFT.In addition, screened film only is formed on thechannel formation region 408 of pixel TFT, but the invention is not restricted to this.Screened film also can be formed on the channel formation region of driving circuit TFT.

Note, can combine with any ofembodiment 1～3 and be used as replenishing embodiment 4.

[embodiment 5]

Embodiment 5 has illustrated an example that is different fromembodiment 1, and this is that opening contact hole is made source lead and drain lead in the second shapegate insulating film 305b,first interlayer dielectric 344,second interlayer dielectric 345 and the 3rd interlayer dielectric 347.Notice that used reference symbol is identical with Fig. 3 A～6 those shown.

Figure 10 represents the sectional view of the liquid crystal display device of embodiment 5.The liquid crystal display device of embodiment 5 and Fig. 5 B those shown difference are the structure of its contact hole.Note, inembodiment 1, set forth some structures except that contact hole, but so about the detailed structurereference implementation scheme 1 of the liquid crystal display device of embodiment 5, be omitted here.

In embodiment 5, for making middle leads 346 insecond interlayer dielectric 345 in the opening contact hole, and went between before 346 on the make, insecond interlayer dielectric 345, be used for making the contact hole ofsource electrode line 348～350 anddrain line 351 and 352.At this moment, contact hole is not opened infirst interlayer dielectric 344 and the second shapegate insulating film 305b.

Then, after making middle leads 346, make the 3rd interlayer dielectric 347.Opening contact hole in the3rd interlayer dielectric 347,first interlayer dielectric 344 and the second shapegate insulating film 305b then, make source lead 348～350 and

drain lead

351 and 352, make with source region 410,422 and 404, drain region 411,421 and 405 anddrain lead 346 to link to each other.

Can make of the structure of above-mentioned embodiment 5 and to be used for and source region 410,422 and 404 and the contact hole that is connected with 405 of drain region 411,421 and need not corrodesecond interlayer dielectric 345, and corrosion has also been oversimplified.

Notice that explanation is with the situation of n channel TFT as pixel TFT in embodiment 5, but the invention is not restricted to this, also can use the p channel TFT as pixel TFT.

Notice that embodiment 5 can combine with in theembodiment 1～4 any.

[embodiment 6]

Embodiment 6 has illustrated substrate and formed the example of optical screen film between the semiconductor layer of TFT.Note, used and the same symbol of part shown in Fig. 3 A～6.

Figure 11 A represents the sectional view of the liquid crystal display device of embodiment 6.The liquid crystal display device of embodiment 6 and Fig. 5 B those shown's difference is that it has screened film 801.Notice that other structures are described in embodiment 1.Therefore, but about the detailed structurereference implementation scheme 1 of the liquid crystal display device of embodiment 6, be omitted here.

In the liquid crystal display device of embodiment 6, screened film 801 is formed on below thesemiconductor layer 304 of pixel TFT.Screened film 801 is overlapping with thechannel formation region 408 of thesemiconductor layer 304 of pixel TFT, and dielectric film (being oxidation film in embodiment 6) 803 is sandwiched in therebetween.

Screened film 801 maskable light, it can use any material, as long as its material can tolerate the temperature of each Technology for Heating Processing step behind the formation screened film.Can use the material that is difficult for printing opacity, as metal and silicon, that use in the embodiment 6 is W.Notice that the thickness of screened film 801 is preferably the magnitude of 0.1～0.5 μ m.And the thickness of oxide film 803 is preferably the magnitude of 0.5～1.5 μ m.In addition, the distance of 304 of screened film 801 and semiconductor layers is preferably the magnitude of 0.1～0.5 μ m.

Notice that though screened film only is formed on below the pixelTFT semiconductor layer 304 of pixel portion in embodiment 6, embodiment 6 is not limited to this structure.Screened film also can be formed on below the

semiconductor layer

302 and 303 of driving circuit TFT equally.

Structure according to above-mentioned embodiment 6 can prevent that light from shining channel formation region by the substrate downside and causing that the TFT off-state current raises.

If oxide film 803 does not have even curface, problem will take place, the semiconductor layer that forms crystallization equably in crystallization process on oxide film 803.Semiconductor layer is directly to be produced on the oxide film 803, therefore, and the best surface of smooth oxide film 803 earlier before forming semiconductor layer.

For example, it is flat that oxide film 803 can be used CMP (chemically mechanical polishing) throwing.Available known method is carried out the CMP polishing.

Potpourri with silicon gel and electrolytic solution in embodiment 6 polishes.When polishing, apply 100kg/cm to polishing plate with electrolytic solution²Pressure.Pressure during polishing can be at 50～150kg/cm²Scope in select.In addition, when polishing, leave the gap of 0.1 μ m between polished surface and polishing plate.

The off-state current and the unevenness that prevents the semiconductor layer crystallization that can suppress TFT according to said structure.

Though embodiment 6 explanations is with the situation of n channel TFT as pixel TFT, the invention is not restricted to this, also can use the p channel TFT as pixel TFT.

Note, can combine as replenishing with in theembodiment 1～5 any to embodiment 6.[embodiment 7]

Embodiment 7 has illustrated the example of making the signal line after making the source signal line again.

Figure 12 A represents the upper surface figure of the liquid crystal display device of embodiment 7.Notice that Figure 12 B is the sectional view that Figure 12 A cuts open along A-A 'line.Reference number 901 is represented the source signal line, andreference number 902 is represented the signal line.The lead-inwire 903 that forms onsignal line 902 times is middle leads, and it andsignal line 902 are overlapping.

Reference number 904 represent pixel TFT, it has semiconductor layer 905.On semiconductor layer 905, make thegate electrode 920 that links to each other with signal line 902.The source region of semiconductor layer 905 utilizes source lead 921 to link to each other withsource signal line 901 with one of drain region, and another of source region and drain region utilizesdrain lead 910 to link to each other with electric capacity lead-in wire 911.Middle leads 903 is linked to each other withfirst interlayer dielectric 923 by the part ofreference number 912 representatives, and middle leads 903,first interlayer dielectric 923 and electric capacity lead-inwire 911 then constitute storage capacitor.

Drain lead 910 links to each other with pixel electrode 909.

According to the present invention, middle leads 903 is formed betweensecond interlayer dielectric 924 and the 3rd interlayer dielectric 925.Like this, can make power lead andsignal line 902 overlapping, but thereby hole diameter enlargement ratio.

[embodiment 8]

Explanation is the crystalline semiconductor film made with the catalytic elements thermal crystallisation method example as semiconductor layer of the present invention in embodiment 8.When using catalytic elements, preferably adopt Jap.P. open Hei7-130652 number and Hei8-78329 number disclosed technology.

Example shown in Figure 13 A and the 13B is that the open Hei7-130652 number disclosed technology of Jap.P. is used for the present invention.On substrate 1201, make silicon oxide film 1202 earlier, make amorphous silicon film 1203 thereon.Be that the nickel acetate solution of 10ppm forms thereon and contains nickel dam 1204 (seeing Figure 13 A) with nickeliferous weight again.

Secondly, in dehydrogenation after 1 hour, 500～650 ℃ of following thermal treatments 4～12 hours, for example 550 ℃ 28 hours, form crystalline silicon film 1205.Thecrystalline silicon film 1205 that obtains like this has extremely superior crystallinity (seeing Figure 13 B).

Moreover the enough selections of the open Hei8-78329 number disclosed technology energy of Jap.P. are mixed catalytic elements and are selected the crystallization amorphous silicon film.Figure 14 A and 14B have illustrated this technology is used for a kind of situation of the present invention.

Onglass substrate 1301, formsilicon oxide film 1302 earlier, makeamorphous silicon film 1303 andsilicon oxide film 1304 then thereon successively.At this moment, the thickness ofsilicon oxide film 1304 is 150nm.

Then needle drawing shape selects to form perforate 1305 onsilicon oxide film 1304, is that the nickel acetate solution of 10ppm is made thereon and containednickel dam 1306 with nickeliferous weight, contacts (seeing Figure 14 A) withamorphous silicon film 1303 and contain 1306 bottoms in perforate 1305 of nickel dam.

Then 500～650 ℃ of following thermal treatments 4～24 hours, for example 570 ℃ 14 hours, form crystalline silicon film 1307.In this crystallization process, the amorphous silicon membrane portions that contacts with nickel is at first by crystallization, then along laterally carrying out crystallization.Thecrystalline silicon film 1307 of Xing Chenging is shaft-like and set acicular crystal like this, all presses specific oriented growth on each crystal macroscopic view wherein.Therefore, this crystallization process has the crystalline advantage (seeing Figure 14 B) of adjustment.

Notice that in two above-mentioned crystallization technology, except that nickel (Ni), following column element also can be used as catalytic elements: germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), plumbous (Pb), cobalt (Co), platinum (Pt), copper (Cu) and gold (Au).

Crystalline semiconductor film (comprising such as crystalline silicon film, crystal germanium silicon fiml) needle drawing shape by above-mentioned fabrication techniques be can be made into the semiconductor layer of crystal TFT.The TFT that makes with the fabrication techniques crystalline semiconductor film ofembodiment 8 has excellent characteristic, thereby very high reliability is arranged.Yet, adopt TFT structure of the present invention, can use the technology ofembodiment 8 to make TFT to greatest extent.

Below with reference to Figure 15 A and 15B an example is described, this is the method with the used making semiconductor layer ofembodiment 1, promptly with the amorphous semiconductor film as initial film, make it to become the crystalline semiconductor film with catalytic elements after, remove the technological process of catalytic elements.The technology of openly openly being put down in writing for Hei10-135469 number with Jap.P. for Hei10-135468 number with Jap.P. inembodiment 8 is as such method.

The technology of above-mentioned Jap.P. record is to utilize the gettering of phosphorus to be used for removing the used catalytic elements of amorphous silicon film crystallization after crystallization.Use this technology, can make the concentration of catalytic elements in the crystalline semiconductor film reduce to 1 * 10¹⁷Atom/cm³Or lower, be preferably 1 * 10¹⁶Atom/cm³Or it is lower.

Here use no alkali glass substrate, typically as the #1737 substrate of Corning company.Be shown in Figure 15 A with the crystallization fabrication techniques basement membrane 1402 shown in the embodiment 4 and the situation of crystalline silicon film 1403.Then, make 150nm thick silicon oxide film 1404 on the surface ofcrystalline silicon film 1403,, form the zone of exposing crystalline silicon film according to the graphic making perforate as mask.Then mix phosphorus, in crystalline silicon film, form the zone 1405 of mixing phosphorus.

Under this situation, if thermal treatment is 5～24 hours in the blanket of nitrogen under 550-800 ℃, for example 600 ℃ 12 hours, the gettering center is played in 1405 in the phosphorus zone of mixing in crystalline silicon, makes the catalytic elements fractional condensation of staying in thecrystalline silicon film 1403 to mixing in the phosphorus district 1405.

Erode the silicon oxide film 1404 of making mask and mix phosphorus district 1405, can make in the crystalline silicon film and reduce to 1 * 10 because of the used catalytic elements concentration of crystallization process¹⁷Atom/cm³Or it is lower.This crystalline silicon film can be used as the semiconductor layer of TFT of the present invention.

[embodiment 9]

The driving method of liquid crystal display device of the present invention has been described.The block diagram of liquid crystal display device example of the present invention is shown in Figure 16.

Reference number 1601 is represented the source signal line drive circuit, andreference number 1602 is represented the signal line drive circuit, andreference number 1603 represent pixel parts.In embodiment 9, respectively form a source signal line drive circuit and a signal line drive circuit, but the invention is not restricted to this structure.Also can form two source signal line drive circuits and two signal line drive circuits.

Source signalline drive circuit 1601 contains shift-register circuit 1601_1, level phase-shift circuit 1601_2 and sample circuit 1601_3.Note, can use the level phase-shift circuit in case of necessity, but be not to use.In addition, in embodiment 9, level phase-shift circuit 1601_2 is formed between shift register 1601_1 and the sample circuit 1601_3, but the invention is not restricted to this structure.Also can use level phase-shift circuit 1601_2 is included in structure among the shift register 1601_1.

Clock signal C L and initial pulse signal SP input to shift-register circuit 1601_1.The sampled signal that vision signal is taken a sample is exported by shift-register circuit 1601_1.The sampled signal incoming level phase-shift circuit 1601_2 of output increases the amplitude of its current potential and exports.

Sampled signal input sampling circuit 1601_3 by level phase-shift circuit 1601_2 output.Meanwhile, vision signal is through video signal cable (not shown) input sampling circuit 1601_3.

The vision signal of input is sampled in sample circuit 1601_3 according to sampled signal, and its result is through the predetermined pixel ofsource signal line 1604 inputs.

Source signal line 1604 links to each other with source signalline drive circuit 1601, and thesignal line 1605 that links to each other with signalline drive circuit 1602 runs through pixel portion 1603.The thin film transistor (TFT) of pixel 1606 (pixel TFT) 1607, liquid crystal are sandwiched in liquid crystal cell between electrode and thepixel electrode 1608 andstorage capacitor 1609 all are formed in

source signal line

1604 and 1605 area surrounded of signal line.

Pixel TFT 1607 is come work according to gating signal, gating signal from signalline drive circuit 1602 through 1605 inputs of signal line.Sampled vision signal inputs to the source signal line of being chosen by pixel TFT 1,607 1604, and writes predetermined pixel electrode simultaneously.

Note,, the invention is not restricted to this though source signalline drive circuit 1601 and signalline drive circuit 1602 all are formed on the substrate of having madepixel portion 1603 in embodiment 9.Source signalline drive circuit 1601 and signalline drive circuit 1602 also can be formed on the IC chip, and link to each other withpixel portion 1603 through FPC or TAB.

In addition, the method for driving liquid crystal display device of the present invention is not limited to the method shown in the embodiment 9.

Any ofembodiment 1～8 at random can be combined with embodiment 9.

[embodiment 10]

Under one group of etching condition ofembodiment 1, carry out first corrosion process and form the first shape conductive layer, but this corrosion process also can carry out under many group etching conditions, with subtracting at film

Vpg connection thin and gate insulating film improves homogeneity.Embodiment 10 is illustrated under two groups of etching conditions carries out the example that first corrosion process forms the first shape conductive layer.

In addition, according to the present invention, the both sides of conductive layer have all formed tapering, and the LDD district is formed on the both sides of channel formation region.Yet embodiment 10 is to come manufacturing process is described according near the enlarged drawing n channel TFT conductive layer one side of driving circuit among Figure 18 A～18D.Note, for the sake of simplicity, not shown basement membrane and substrate.

At first, obtained the state identical according toembodiment 1 with Fig. 3 B.Yet, though

Use Ta as first conducting film in theembodiment 1, have the TaN of ultrahigh heat-resistant characteristic as first conducting film but in embodiment 10, use.The first conduction thickness, the 20～100nm that makes, and the second conducting film thickness of making can be 100～400nm.In embodiment 10, thick is TaN first conducting film and thick W second conducting film formation lamination for 370nm of 30nm.

Secondly, form thefirst shape mask 1505a, corrode, make first shape, thesecond conducting film 1504a with ICP by resist.Here use CF₄, Cl₂And O₂Potpourri as etchant gas, therefore it has high selectivity to TaN, has obtained the state shown in Figure 18 A.Several etching conditions and be shown in table 1 with the relation of second conductive layer (W) corrosion rate, first conductive layer (TaN) corrosion rate and second conductive layer (W) cone angle.

[table 1] W and TaN corrosion rate (E.R.) and W cone angle

Condition	????ICP	Bias voltage	Pressure	???CF₄	???Cl₂	???O₂	W corrosion rate (1) [nm/min]	TaN corrosion rate (2) [nm/min]	W/TaN selects than (1)/(2)	W cone angle [degree]
	????ICP	Bias voltage	Pressure	???CF₄	???Cl₂	???O₂					????[W]	???[W]	????[Pa]	?????????????????????????[sccm]
	???1	????500	???20	????1.0	????30	????31					????[W]	???[W]	????[Pa]	?????????????????????????[sccm]			???0	????58.97	????66.43	?????0.899	????80
???2	???1	????500	???20	????1.0	????30	????31	????500	???60	????1.0	????30	????30	???0	????88.71	????118.46	?????0.750	????25	???0	????58.97	????66.43	?????0.899	????80
???2	???3	????500	???100	????1.0	????30	????30	????500	???60	????1.0	????30	????30	???0	????88.71	????118.46	?????0.750	????25	???0	????111.66	????168.03	?????0.667	????18
???4	???3	????500	???100	????1.0	????30	????30	????500	???20	????1.0	????25	????25	???10	????124.62	????20.67	?????6.049	????70	???0	????111.66	????168.03	?????0.667	????18
???4	???5	????500	???60	????1.0	????25	????25	????500	???20	????1.0	????25	????25	???10	????124.62	????20.67	?????6.049	????70	???10	????161.72	????35.81	?????4.528	????35
???6	???5	????500	???60	????1.0	????25	????25	????500	???100	????1.0	????25	????25	???10	????176.90	????56.32	?????3.008	????32	???10	????161.72	????35.81	?????4.528	????35
???6	???7	????500	???150	????1.0	????25	????25	????500	???100	????1.0	????25	????25	???10	????176.90	????56.32	?????3.008	????32	???10	????200.39	????80.32	?????2.495	????26
???8	???7	????500	???150	????1.0	????25	????25	????500	???200	????1.0	????25	????25	???10	????218.20	????102.87	?????2.124	????22	???10	????200.39	????80.32	?????2.495	????26
???8	???9	????500	???250	????1.0	????25	????25	????500	???200	????1.0	????25	????25	???10	????218.20	????102.87	?????2.124	????22	???10	????232.12	????124.97	?????1.860	????19
???10	???9	????500	???250	????1.0	????25	????25	????500	???20	????1.0	????20	????20	???20	??????-	????14.83	???????-	????-	???10	????232.12	????124.97	?????1.860	????19
???10	???11	????500	???60	????1.0	????20	????20	????500	???20	????1.0	????20	????20	???20	??????-	????14.83	???????-	????-	???20	????193.02	????14.23	?????13.695	????37
???12	???11	????500	???60	????1.0	????20	????20	????500	???100	????1.0	????20	????20	???20	????235.27	????21.81	?????10.856	????29	???20	????193.02	????14.23	?????13.695	????37
???12	???13	????500	???150	????1.0	????20	????20	????500	???100	????1.0	????20	????20	???20	????235.27	????21.81	?????10.856	????29	???20	????276.74	????38.61	?????7.219	????26
???14	???13	????500	???150	????1.0	????20	????20	????500	???200	????1.0	????20	????20	???20	????290.10	????45.30	?????6.422	????24	???20	????276.74	????38.61	?????7.219	????26
???14	???15	????500	???250	????1.0	????20	????20	????500	???200	????1.0	????20	????20	???20	????290.10	????45.30	?????6.422	????24	???20	????304.34	????50.25	?????6.091	????22

^*) in the table "-" represent not energy measurement because the W surface is destroyed in corrosion.

Notice that the cone angle in this instructions is represented the angle between material layer side and surface level, shown in Figure 18 A top right plot.And for convenience's sake, will have the side of cone angle to be called taper in this manual, there is the part of taper to be called tapering part.

And, for example, using a kind of in the condition 4～15 of table 1 as first group of etching condition, the angle (cone angle 1) that forms between second conductive layer (W) side and surface level freely can be fixed in 19～70 ° the scope.Notice that etching time can suitably be determined by the operator.

In addition,reference number 1501 is represented semiconductor layer in Figure 18 A, andreference number 1502 is represented gate insulating film, andreference number 1503 is represented first conducting film.

Then, keepmask 1505a, under second group of etching condition, corrode, form first shape, the first conductive layer 1503a.Notice that when corroding,gate insulating film 1502 also is corroded some and becomes the first shape gate insulating film 1502a under second group of etching condition.Here use CF₄And Cl₂Mixed gas as the etchant gas under second group of etching condition.For example, any in thecondition 1～3 all can be used as second group of etching condition in the table 1.Therefore under two groups of etching conditions, carry out first corrosion process, but the attenuate (seeing Figure 18 B) ofsuppressor dielectric film 1502 just.

Notice that when corroding, first shape, the secondconductive layer 1504a among Figure 18 B also is corroded under second group of etching condition.But etching extent is small (about 0.15 μ m, promptly total live width 0.3 μ m), so person shown in the figure and Figure 18 A have same shape.

Next step keepsmask 1505a and carries out second corrosion process, obtains the second shape conductive layer shown in Figure 18 C.Second corrosion process in the embodiment 10 is to use CF₄, Cl₂And O₂Those etching conditions of mixed gas under corrode.In the condition 4～15 of table 1 any all can be used as the etching condition here, and etching time can suitably be determined.And, each conductive layer along raceway groove longitudinally width can freely stipulate according to etching condition.Second shape

Mask 1505b, second shape, the firstconductive layer 1503b, second shape, the secondconductive layer 1504b and the second shapegate insulating film 1502b are made by second corrosion process.

Notice that second shape, the firstconductive layer 1503b is corresponding to first grid electrode in embodiment 10, the secondconductive layer 1504b is corresponding to second gate electrode for second shape.

The cone angle 2 that forms in second shape, the secondconductive layer 1504b is greater thancone angle 1, and formed minimum cone angle beta in second shape, the firstconductive layer 1503b.

Then, keepmask 1505b and carry out the first doping process (seeing Figure 18 C).Here make mask with second shape, the secondconductive layer 1504b, mix n type conductive impurity phosphorus with ion doping normal direction semiconductor layer 1501.In addition, the first doping process is to carry out under the situation that keepsmask 1505b, but also can carry out the first doping process after removingmask 1505b.

Impurity range

1501a and 1501b are formed by the first doping process.In addition, the semiconductor layer and second conductive layer are overlapping, and the gate insulating film and first conductive layer are sandwiched in therebetween, and this part of semiconductor layer then becomes channel formation region.Notice that though not shown,

impurity range

1501a and 1501b are formed on the both sides of channel formation region, and are rotational symmetry (linear symmtry).

In addition, the thickness of the material layer of arranging on semiconductor layer is thick more, and the depth of penetration of dopant ion is just shallow more during doping.Therefore, overlapping with first conductive layer, gate insulating film is sandwiched inimpurity range 1501a therebetween, that is a LDD district (Lov district) be subjected to sidewall to have the influence of the tapering part of cone angle beta, and the impurity concentration of mixing semiconductor layer changes.Film is thick more, and impurity concentration is low more, and film is thin more, and impurity concentration is high more.

In addition, when carrying out second corrosion process, according to etching condition, also such situation can be arranged, promptly tapering part is formed in the gate insulating film, in this case, semiconductor layer also is subjected to the influence of this tapering part, and the impurity concentration of mixing semiconductor film also changes.

On the other hand, at not overlapping with first conductivelayer impurity range 1501b, that is in the 2nd LDD district (Loff district), the thickness of gate insulating film is almost constant, thereby the impurity concentration in the 2nd LDD district (Loff district) also is almost constant.

Next step though do not illustrate among the figure, forms the Etching mask that covers pixel TFT.Here, determine the Loff section length of pixel TFT by the size of control Etching mask.

Then carry out the second doping process.Making mask with second shape, firstconductive layer 1503b and second shape, the secondconductive layer 1504b, mix the impurity element that is a kind of conduction type with the ion doping method insemiconductor layer 1501, is n type conductive impurity phosphorus here.The doping content of the second doping process is higher than the first doping process, and formsimpurity range 1501C and 1501d.

Except the impurity concentration of mixing by the first doping process,impurity range 1501d, i.e. source region or drain region are because of the second doping process has higher concentration.

And impurity range 1501C does not mix, because it and first conductive layer are overlapping, and has the Impurity Distribution identical with impurity range 1501a.Therefore impurity range 1501C also is a LDD district.Yet relevant with doping condition, impurity range 1501C can have higher concentration.In this case, the second doping process is also as the first doping process, and the impurity that mixes in the semiconductor layer is subjected to sidewall to have the influence of the tapering part of cone angle beta.

On the other hand, only do not mixed, form source region or drain region by the zone that Etching mask covers in pixel TFT.Covered by Etching mask and then do not remain unchanged with overlapping the2nd LDD district 1501b of conductive layer.

Then remove the Etching mask of switching TFT.

The active matrix substrate of Fig. 6 B can be begun to make step by step by Fig. 4 C according to the technological process ofembodiment 1.

Make driving circuit n channel TFT and pixel TFT respectively according to above-mentioned method.

Driving circuit n channel TFT contains: form the district with the second conductive layer trench overlapped, gate insulating film is sandwiched in therebetween; The one LDD district is in the channel formation region both sides; Source region or drain region contact with a LDD district.Pixel TFT contains: form the district with the second conductive layer trench overlapped, gate insulating film is sandwiched in therebetween; The one LDD district is in the channel formation region both sides; The 2nd LDD district contacts with a LDD district; Source region or drain region contact with the 2nd LDD district.

And a LDD district and first conductive layer are overlapping, and gate insulating film is sandwiched in therebetween, and its impurity concentration increases with the distance of distance channel formation region.Notice that a zone is arranged, and its impurity concentration gradient is at least 1 * 10 in a LDD district¹⁷～1 * 10¹⁸Atom/cm³Scope.If the LDD district has so continuous CONCENTRATION DISTRIBUTION, can reduce off-state current effectively.And length is big more longitudinally along raceway groove in a LDD district, and reliability is high more.

In fact, the boron that in the zone 149～152 of driving circuit p channel TFT, mixes by boron doping process (seeing Fig. 4 C), with the first doping similar process, also be subjected to the influence of first conductive layer thickness, this one deck on semiconductor layer has a tapering, thereby the impurity concentration of mixing impurity range changes.Film is thick more, and impurity concentration is low more, and film is thin more, and impurity concentration is high more.

Note, can at random embodiment 10 any withembodiment 1～9 be combined.

And, as the etchant gas (CF of embodiment 10₄And Cl₂Mixed gas) replace SF₆And Cl₂Mixed gas, or work as CF₄, Cl₂And O₂Mixed gas replace SF₆, Cl₂And O₂Mixed gas the time, the selectivity ofgate insulating film 1502 is high, so the attenuate of film more can further be suppressed.

[embodiment 11]

According to various etching conditions, write down as enforcement scheme 10, the second shape first grid electrode (TaN) can have different shapes.In embodiment 11, the shape B of the shape A of Figure 19 A and Figure 19 B is simulated and compares.

Shape A shown in the embodiment 10 is shown in Figure 19 A.Figure 19 A is the same with Figure 18 D, has therefore used identical reference symbol.Figure 20 is the graph of a relation of expression electron temperature and first grid electrode thickness, and Lov section length (along raceway groove Lov section length longitudinally) is got 0.4 μ m, 0.8 μ m and 1.5 μ m, and first grid electrode thickness is 15～40nm in Figure 19 A.Notice that simulation is to carry out with the vertical impurities concentration distribution of raceway groove shown in Figure 23 (CONCENTRATION DISTRIBUTION of 10nm depths under the semiconductor layer surface).Yet simulation is to do under the situation that first grid electrode lateral parts has cone angle to change, and the part of change is in the thickness scope of first grid electrode 10nm from section, from upper surface, is in the scope of first grid electrode edge part 0.13 μ m.

In addition, Figure 19 B represents the shape B of embodiment 11.Figure 19 B is different from Figure 19 A, the position that lateral parts does not have cone angle to change.Just formed cone angle gamma.

The simulation thatfirst grid electrode 1700 is carried out equally is shown in Figure 19 B, and the relation of electron temperature and first grid electrode (TaN) thickness is shown in Figure 21, and the Lov section length is 0.4 μ m, 0.8 μ m and 1.5 μ m, and first grid electrode thickness is 15～40nm.Notice that simulation is to carry out with the vertical impurities concentration distribution of raceway groove shown in Figure 23.

In addition, for thefirst grid electrode 1700 shown in Figure 19 B, when the TaN thickness was 30nm, the relation of raceway groove longitudinal electric field intensity and Lov section length and the relation of Lov section length and electron temperature were shown in Figure 22.The electric field intensity shown in Figure 22 and the variation tendency of electron temperature are much at one.Therefore, we can say that this expression electron temperature is low more, the trend that TFT degenerates is weak more.

When comparing Figure 21 and Figure 22, the shape of Figure 19 B shown in Figure 21 shows lower electron temperature.In other words, from the viewpoint that TFT degenerates, preferably use the shape of Figure 19 B, because electron temperature can reduce.

In addition, when the Lov section length was 1.5 μ m, electron temperature was low, therefore can infer, long Lov district is preferred.

Any ofembodiment 1～10 at random can be combined with embodiment 11.

[embodiment 12]

Liquid crystal display device of the present invention can be used as the display media of various electronics equipments.

Can provide such electronics equipment below: gamma camera, digital camera, projector (back projection type or front projection type), head-mounted display apparatus (goggle type display device), game machine, Vehicular navigation system, personal computer, pocket information terminal (as automobile computer, mini phone or e-book) etc.Some instantiations of electronics equipment are shown in Figure 17 A～17F.

Figure 17 A represents a kind of image display, comprisesshell 2001, bearing 2002,display part 2003 etc.The present invention can be used for itsdisplay part 2003.

Shown in Figure 17 B is gamma camera, comprisesmain body 2101,display part 2102,audio frequency importation 2103, operatingswitch 2104,battery 2105 and image receiving unit 2106.The present invention can be used for itsdisplay part 2102.

Figure 17 C is depicted as the part (right-hand part) of head-mounted display device, comprisesmain body 2201,signal cable 2202,headband 2203,screen portions 2204,optical system 2205,display part 2206 etc.The present invention can be used for itsdisplay part 2206.

What Figure 17 D represented is the picture reproducer (particularly, DVD player) that contains recording medium, comprises main body 2301, recording medium (as DVD) 2302, operating switch 2303, display part (a) 2304, display part (b) 2305 etc.Display part (a) 2304 is mainly used in displays image information, and display part (b) 2305 is mainly used in character display information.The present invention can be used for its display part (a) 2304 and (b) 2305.Notice that the picture reproducer that contains recording medium also comprises as the family game machine etc.

Figure 17 E represents personal computer, comprisesmain body 2401,image importation 2402,display part 2403 and keyboard 2404.The present invention can be used for itsdisplay part 2403.

Figure 17 F represents the goggle type display device, comprises that main body 2501, display part 2502 and mirror shank divide 2503.The present invention can be used for its display part 2502.

As mentioned above, range of application of the present invention is extremely broad, the present invention can be used for the electronics equipment in all fields.And the electronics equipment of embodiment 12 can be realized with the combination in any ofembodiment 1～11.

As mentioned above, the length (after this abbreviating gate electrode width as) of vertical (carrier moving direction) first and second gate electrodes of raceway groove of the present invention is different.Therefore, when carrying out the ion injection as mask with first and second gate electrodes, the ion depth of penetration differences that utilization causes because of gate electrode thickness is different can make the ion concentration in the semiconductor layer below second gate electrode be lower than below first grid electrode but the ion concentration in the semiconductor layer under second gate electrode not.In addition, also can make below first grid electrode but not the ion concentration in the semiconductor layer under second gate electrode be lower than ion concentration in the semiconductor layer below first grid electrode not.

In addition, in order to form the Loff district with mask, need only control the width of the first grid electrode and second gate electrode with corrosion.Compare with the example of routine, the position in control Loff district and Lov district has become easily.Therefore, TFT with desirable characteristics of the accurate location in Lov district and Loff district and making has also just become easily.

In addition, middle leads is produced between second interlayer dielectric and the 3rd interlayer dielectric.Therefore, middle leads can do with signal line or source signal line overlap, but thereby hole diameter enlargement ratio.